This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Small trees or shrubs with alternate simple deciduous leaves and white racemose flowers. Calyx urceolate; lobes persistent. Berry imperfectly 4- to 10-celled; cells 1-seeded. Only four species are known, but they are widely dispersed, occurring in the Mediterranean region, Japan, and North America. Amelanchier is the Savoy name of the Medlar. A. vulgaris and A. Canadensis with their varieties are elegant small trees with oblong, oval or nearly orbicular toothed leaves and white racemose flowers in early Spring. Some of the varieties are very hairy when young, but eventually become glabrous. A. spicatus, A. Botryapium, A. ovalis, etc, are slight varieties. In fact, we have been unable to find constant characters to separate European and American forms. Those adduced by Koch break down when tried with a complete series of specimens.